Medical systems including medical devices that are implantable (IMD) or external and associated implantable medical leads provide functions such as stimulation of muscle or neurological tissue and/or sensing of physiological occurrences within the body of a patient. Typically, the IMD is installed in a subcutaneous location that is accommodating and relatively accessible for implantation. For instance, to provide stimulation near the spine or pelvis, the IMD may be installed in a pocket located on the abdomen or upper buttocks region of the patient. The external device may be located in the same area but outside of the body. The implantable medical lead is installed, either through a percutaneous procedure or a surgical procedure, depending upon the type of lead that is necessary.
Once installed, the lead extends from the stimulation site to the location of the IMD or external device. The separation of the stimulation site to the location of the device varies, but may typically range from about 20 cm to about 100 cm. For relatively lengthy separation, if a lead of adequate length is unavailable then a lead extension may be implanted to span from the device to a proximal end of the implantable lead.
The implantable medical lead includes electrical connectors on a proximal end, electrodes on a distal end, and conductive filars interconnecting the connectors to the electrodes. When an extension is present, the implantable extension includes a connector block on the distal end that connects to the proximal connectors of the lead and includes connectors on the proximal end that connects to the device.
Each connector ring of the proximal end of the lead or extension that is being inserted into the header of the device needs to have a proper electrical connection to an electrical connector within the device. If the electrical connection for each connector of the lead or extension is not proper, then short circuits and/or open circuits may exist between the individual stimulation pathways, where the device may attempt to apply a custom stimulation signal to each simulation pathway during therapy. The short circuits and/or open circuits may adversely affect the stimulation therapy and/or may cause other problems such as reduced battery lifetime due to increased current drain.
Additionally, implantable medical systems are being developed to allow patients having such implantable medical systems to undergo an MRI scan. One manner of doing so may be to include a shield that grounds through a connector that establishes an electrical connection in the header of the device similar to the stimulation connectors. If this ground connector is not properly connected during lead insertion, then the shield may not perform as expected during an MRI scan.
Conventional attempts to verify proper lead insertion involve manually initiating a single lead impedance measurement after the connections have been made. However, waiting until the lead is inserted to manually initiate a impedance test does not provide feedback while the physician is inserting the lead, and the physician is at risk of attempting to insert the lead too far, potentially over-inserting the lead to prevent proper connection, or damaging the lead by kinking the lead due to continued force on the lead after the lead is fully inserted. This lack of feedback can also lead to a trial-and-error technique, where the physician is not sure about the proper insertion and can under insert the lead on the first attempt, which causes additional handling of the device after the measurement is taken in order to re-insert the lead.